wild red oat vs oat

wild red oat and oat both are nouns.

Word	Noun	Adjective	Verb	Adverb
wild red oat	Yes	No	No	No
oat	Yes	No	No	No

As nouns, oat is a hypernym of wild red oat; that is, oat is a word with a broader meaning than wild red oat:

wild red oat: Mediterranean oat held to be progenitor of modern cultivated oat
oat: annual grass of Europe and North Africa; grains used as food and fodder (referred to primarily in the plural: `oats')

wild red oat (noun)	oat (noun)
Mediterranean oat held to be progenitor of modern cultivated oat	seed of the annual grass Avena sativa (spoken of primarily in the plural as `oats')
	annual grass of Europe and North Africa; grains used as food and fodder (referred to primarily in the plural: `oats')